Method and apparatus for treating concrete with a partial vacuum



April 14, 1970 J. J. cREsKoFF 3,506,747

METHOD AND APPARATUS vFOR TREATING CONCRETE WITH A `PARTIAL VACUUM Filed Jan.' 30, 1968 2, Sheets-Sheet l nwe/v ron JA cos J CRES/forf- Cawwf/,MP/,mwwa/Mm/ ATTORNEYS J. J. cREsKoFF 3,506,747 METHOD AND APPARATUS FOR TREATING CONCRETE April 14, 1970 WITH A `PARTIAL VACUUM 2 Sheets-Sheet 2 Filed Jan. 30, 1968 /NVE/VTOR JACOB J. CRES/(OFF ATTORNEYS.

United States Patent O U.S. Cl. 264-87 6 Claims ABSTRACT OF THE DISCLOSURE An improved method and apparatus for treating concrete. An apparatus is provided which comprises a cover, a first member which is provided about the periphery of the cover to form an outer compartment under the cover and a second member which is provided within the first member to provide an inner compartment within the member. Means defining a port are provided for connecting the inner compartment to a source of reduced pressure. Means defining fluid passages between the inner compartment and the outer compartment are also provided which are smaller in area than the port. This apparatus is used for vacuum treating concrete having excess water. The improved results from the fact that the smaller inner compartment is easier sealed to the concrete than the outer compartment and once sealed it causes the outer compartment to seal.

This invention relates to treating concrete and more particularly to a method and apparatus for vacuum processing concrete.

Vacuum processing of Wet concrete enables the rapid drying of the concrete which results in a substantial increase in the strength of the concrete and also produces a concrete having an improved texture because considerably less volume change takes place in the drying of the concrete. There is also a reduction in the formation of cracks in concrete so processed.

The various advantages of vacuum processed concrete are set forth in the Billner Patent No. 2,046,867 issued July 7, 1936.

Heretofore existing vacuum mats for treating concrete have required aps around the perimeter of the vacuum mat to enable seating of the vacuum mat against the concrete when the vacuum is applied to the mat. That is, unless a seal is completed about the entire periphery of the vacuum mat, the atmospheric pressure which enters the compartment beneath the mat prevents a vacuum from being formed and thereby prevents the seating of the vacuum mat on the unprocessed concrete. For this reason, very large pumps are required in order to maintain a reduced pressure underneath the vacuum mat until the vacuum mat is seated and a seal is formed about the periphery thereof.

The provision of iiaps around the perimeter of the prior vacuum mat aid the seating of the vacuum mat, but there remain disadvantages with flaps. In most applications, a man must jump on the top of the vacuum mat in order to accomplish seating. Moreover, after Ithe vacumat is seated, the flaps around the perimeter of the vacuum mat cause ridges in the wet concrete. These ridges are difficult to eliminate after the concrete is set.

It is therefore an object of the invention to overcome the aforementioned disadvantages.

Another object of the invention is to provide a new and improved vacuum mat which is easily seated for treating concrete.

Another object of the invention is to provide a new and improved vacuum mat for treatin-g concrete which 3,506,747 Patented Apr. 14, 1970 requires smaller pumping facilities for providing a vacuum underneath said mat.

Another object of the invention is to provide a new and improved method and apparatus for treating concrete which utilizes a vacuum mat having two concentric constantly communicating compartments, with the inner compartment of said mat being smaller than the outer compartment.

Another object of the invention is to provide a new and improved vacuum mat for treating concrete which facilitates seating of the vacuum mat on the concrete notwithstanding variations in the surface of the concrete surface.

These and other objects of the invention are achieved by providing a method and apparatus for treating concrete which comprises providing a vacuum mat having a cover, a first member provided about the periphery of the cover to form an outer compartment under the cover and a second member provided within the first member to form an inner compartment under the cover. Means defining a port are provided for connecting the inner compartment to a source of reduced pressure. Means defining a uid passage between the inner compartment and the outer compartment are also provided which are smaller in area than the port.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of the bottom portion of a vacuum mat embodying the invention;

FIG. 2 is a perspective view of the top portion of the vacuum mat embodying the invention;

FIG. 3 is an enlarged exploded perspective view which is partially fragmentary showing the assembly of the various components comprising the vacuum mat; and

FIG. 4 is a sectional view taken along line 4 4 of the vacuum mat embodying the invention on a section of freshly poured concrete.

Referring now in greater detail to the various figures of the drawing wherein similar reference characters refer to similar parts, a vacuum mat embodying the invention for use in treating concrete is shown generally at 20 in FIG. 1.

Vacuum mat 20 basically comprises a cover 22. Cover 22 is planar and rectangular and is preferably comprised of molded fiberglass. The cover 22 includes an integral first member which forms a gasket 24 which extends entirely about the periphery of the cover 22 and depends from the lower surface of the cover 22.

As best seen in FIG. 3, a second member which comprises a plurality of non-resilient, non-compressible and non-deformable gasket strips 26, 28, 30 and 32 is adhesively secured to the lower surface of cover 22 to form the periphery of an inner compartment which is concentric with the compartment defined by gasket 24.

Strips 28 and 32 are parallel to each other and to two sides of gasket 24. The strips 26 and 30 are parallel to each other and to the remaining two walls of gasket 24 and extend between and perpendicular to strips 28 and 32. Strips 26 and 30 extend intermediate of strips 28 and 32 and thereby form fluid passages or ports 34, 36 and 38, 40 between the ends of the strips 26 and 30` and the ends of strips 28 and 32.

A channel 42 is provided in the lowermost surface of the gasket which extends along the entire length 0f the gasket 24. A port comprised of an opening at the center of cover 22 in which a pipe 44 is suitably secured is provided in the inner compartment. The pipe 44 is connected via suitable valves to a source of reduced pressure such as a vacuum pump and enables communication between the inner compartment formed between gaskets 26 through 32 and the source of reduced pressure.

It can therefore be seen that two open compartments are provided. An outer first compartment is formed between gasket 24 and the periphery of gaskets 26 through 32. An inner second compartment is formed within the periphery of gaskets 26 through 32.

The inner compartment and the outer compartment are constantly communicating because of ports 34 through 38. The aggregate area of ports 34 through 38 is smaller than the area of the port defined by pipe 44. Therefore, where pipe 44 is connected to a vacuum supply and the gaskets 26 through 32 are in contact with a planar surface, which thereby closes the inner compartment, a partial vacuum is formed in the inner compartment because the flow of fluid through pipe 44 is greater than through ports 34 through 38. As will hereinafter be seen, this action enable the inner compartment to cause the entire vacuum mat to be sealed against freshly poured concrete;y

A first metal lath 46 which is comprised of two pieces 48 and 50 and which is preferably comprised of expanded metal are placed in the first and second compartments, respectively, of the vacuum mat. Thus, portion 48 is placed within the first compartment defined by the gasket 24 and the gaskets 26 through 32; and, portion 50 of the metal lath is provided within the inner compartment defined by gaskets 26 through 32. A fly screen 52 comprised of portions 54 and 56 is placed beneath the metal lath 46 within the vacuum mat. Portion 54 is placed in the outer compartment underneath portion 48 of the metal lath and portion 56 is placed beneath portion 50 of the metal lath.

A filter cloth 58 is provided beneath the lath 46 and screen 52 which extends over substantially the entire bottom surface of the vacuum mat. The filter cloth 58 is maintained in place by a spline 60 which is press-fit into the channel 42 over the filter cloth 58 adjacent the periphery thereof.

The metal lath 48 and fly screen 54 enable the uniform distribution of pressure throughout the first and second compartments of the mat when it is vacuum sealed to the concrete and treating the same. The filter cloth 58 is preferably made of a fine mesh which permits water to pass through but does not allow the solid particles from a cement mass to pass through.

The vacuum mat also includes a pair of lugs 62 which are preferably placed on opposite sides of the top surface of the cover aligned with pipe 44. Lugs 62 pro-ject upwardly from the top surface of cover 22 and include integral transversely extending legs 64 which are embedded in the fiberglass cover. The lugs include openings 66 for the reception of hooks or cables for cooperation with a crane or other lifting device for placement of the vacuum mat on the surface of the concrete.

The combined area of the ports 34 through 40 is smaller than the area of the port defined by pipe 44. Thus when cover 22 is placed on freshly poured concrete, a partial vacuum is first formed in the inner compartment defined between gaskets 26 through 32. As a seal is formed between gaskets 26 through 32 and the concrete, the communication of uid through ports 34 through 40 distributes the partial vacuum to the compartment defined between gasket 24 and the outer periphery of gaskets 26 and 32.

Operation of the vacuum mat embodying the invention for treating a body of concrete 70 is best seen in FIG. 4. The vacuum mat is placed on the top surface of the concrete 70. The pipe 44 is then connected to a vacuum supply. A partial vacuum which is preferably 28 inches of mercury is formed in the small inner compartfment which thereby causes the atmospheric pressure to compress the cover 22 against the concrete. The cover is thereby urged a fraction of an inch against the surface of the concrete 70 which causes contact between gasket 24 and the surface of the concrete. The contact between gasket 24 and the concrete seals off the outer compartment of the vacuum mat 22. The vacuum supply which is admitted from the inner compartment into the outer compartment via the ports 34 through 40 then causes a partial vacuum in the outer compartment as well. The vacuum supply is applied to the inner and outer compartments until the concrete 70 has been completely treated. The vacuum mat 20 is then removed.

In addition to the ease of seating of the vacuum mat, the inner compartment in the vacuum mat reduces the cost of vacuum processing in that a smaller vacuum supply is required. That is, in order to vacuum process concrete, an adequate vacuum supply must be available to create a partial vacuum in the following elements:

(1) in the vacuum mat;

(.2) in the concrete under the mat;

(3) to counteract the losses in vacuum due to the porosity of the concrete mix; and

(4) to counteract the loses about the perimeter of the mat due to the poor fit between the vacuum mat and the concrete surface which is caused by irregularity in the surface of the concrete.

Of these four elements, it has been found that the largest vacuum supply is required for the fourth element which accomplishes initial contact between the vacuum mat and the concrete surface.

Since the deviation between the plane of the small inner compartment and the concrete surface under it is less than the deviation between the plane of the entire vacuum mat and the entire concrete surface under the mat, a smaller vacuum supply is necessary to cause initial contact between the gasket member of the small inner compartment than is required to cause initial contact of the gasket for the entire outer compartment with the concrete.

As soon as contact is provided between the inner compartment and the concrete, the atmospheric pressure causes immediate contact between the entire undersurface of the vacuum mat and the concrete mix as the inner compartment is pressed against the surface of the concrete.

Experimental work has indicated tht satisfactory results may be achieved when the ratios of the areas of the entire vacuum mat area to the area of the inner compartment are between the ratios of 2:1 to 25:1. A preferred area ratio has been found to be 12:1 of the whole mat to the inner compartment.

Experimental Work has also indicated that the ratio of the area of the port defined by the inner bore of pipe 44 to the aggregate area of the fluid passage means provided by ports 34 through 40 is preferably in the range of ratios of 6 and 12.

While my invention is intended primarily for the treatment of concrete placed in horizontal layers such as floors, roads, etc., it should be understood that the invention is not limited to such use and may be employed for the treatment of concrete shapes intended for other purposes such as vertical walls, columns and pipes.

Without further elaboration, the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, readily adapt the same for use under various -conditions of service.

What is claimed as the invention is:

1. In an apparatus for treating wet concrete which comprises in combination, a cover, a first member provided about the periphery of said cover to form an outer compartment under said cover, and a lter member which prevents solid particles from entering said compartment, the improvement comprising a second member provided under said cover and centrally thereof to form an inner compartment, said inner compartment having an area between the ratios of 1:2 to 1:25 of the entire area under said cover, means defining a port for connecting said inner compartment to a source of reduced pressure, said apparatus being secured to concrete by placing said cover on said wet concrete and applying a partial vacuum to said inner compartment, said second member including means defining a uid passage means between said inner compartment and said outer compartment, said lluid passage means having an area within the ratios of 1:6 and 1:12 of the area of said port so that said partial vacuum is first formed in said inner compartment and then provided to said outer compartment, said partial vacuum in said inner compartment enabling atmospheric pressure to seat said entire cover against said concrete.

2. The invention of claim 1 wherein said lirst member and said second member are comprised of a relatively noncompressible material, said second member comprising a plurality of strips which are concentric with and parallel to the sides of said rst member.

3. The invention of claim 2 wherein said liuid passage means are formed by providing spaces between said ,stripsl comprising said second member.

4. The invention of claim 1 wherein pressure distribution means are provided in said outer and inner compartments, said pressure distribution means comprising a plurality of layers of screening.

5. In a method for treating concrete wherein a cover is provided having a peripheral member to form a rst compartment under the cover, and a lter member to prevent solid particles from entering said compartment, the improvement which comprises providing a second compartment under said cover and centrally thereof having an area between the ratios of 1:2 and 1:25 of the entire area under said cover, setting said cover upon concrete having excess water, connecting said second compartment to a source of reduced pressure, wherein fluid passage means are provided in the wall between said rst compartment and said second compartment of said cover, said aggregate area of said uid passage means being within the ratios of 1:6 and 1:12 of the area connecting said second compartment to a source of reduced pressure, said reduced pressure being applied to said first compartment via said uid passage means, providing a partial vacuum in said second compartment toenable atmospheric 4'pressure to press said cover againstsaid concrete and-fform a seal about both said compartments whereby thepressure in both compartments is `reduced below atmospheric pressure for the purpose of removing excess water from said concrete.

6. The invention of claim 5 wherein means are provided within said rst and said second compartment to provide equal distribution of said reduced pressure throughout said rst and second compartments.

References Cited UNITED STATES PATENTS 2,046,867 7/ 1936 Billner 264-87 2,524,419 10/ 1950 Billner 264-87 2,533,263 12/1950 `Johnson 264-87 2,650,409 9/1953 Dubbs 264-87 2,895,706 7/ 1959 Blatherwick 248-363 3,033,298 5/1962 Johnson 248-363 3,377,096 4/1968 Wood 248-363 IULIUS FROME, Primary Examiner I. H. MILLER, Assistant Examiner U.S. Cl. X.R. 

